1. Field of the Invention
A The invention relates generally to the field of immunology and immunotherapy applications using oligonucleotide-based compounds as immune modulatory agents. More particularly, the invention relates to chemically-modified oligonucleotide-based compounds that modulate immune regulation through TLRs and methods of use thereof.
2. Summary of the Related Art
The immune response involves both an innate and an adaptive response based upon the subset of cells involved in the response. For example, the T helper (Th) cells involved in classical cell-mediated functions such as delayed-type hypersensitivity and activation of cytotoxic T lymphocytes (“CTL”s) are Th1 cells, whereas the Th cells involved as helper cells for B-cell activation are Th2 cells. The type of immune response is influenced by the cytokines and chemokines produced in response to antigen exposure. Cytokines provide a means for controlling the immune response by affecting the balance of T helper 1 (Th1) and T helper 2 (Th2) cells, which directly affects the type of immune response that occurs. If the balance is toward higher numbers of Th1 cells, then a cell-mediated immune response occurs, which includes activation of cytotoxic T cells (e.g. CTLs). When the balance is toward higher numbers of Th2 cells, then a humoral or antibody immune response occurs. Each of these immune responses results in a different set of cytokines being secreted from Th1 and Th2 cells. Differences in the cytokines secreted by Th1 and Th2 cells may be the result of the different biological functions of these two T cell subsets.
Th1 cells are involved in the body's innate response to antigen (e.g. viral infections, intracellular pathogens, and tumor cells). The initial response to an antigen can be the secretion of IL-12 from antigen presenting cells (e.g. activated macrophages and dendritic cells) and the concomitant activation of Th1 cells. The result of activating Th1 cells is a secretion of certain cytokines (e.g. IL-2, IFN-gamma and other cytokines) and a concomitant activation of antigen-specific CTLs. Th2 cells are known to be activated in response to bacteria, parasites, antigens, and allergens and may mediate the body's adaptive immune response (e.g. IgM and IgG production and eosinophil activation) through the secretion of certain cytokines (e.g. IL-3, IL-4, IL-5, IL-6, IL-9, IL-10, IL-13 and other cytokines) and chemokines. Secretion of certain of these cytokines may result in B-cell proliferation and an increase in antibody production. In addition, certain of these cytokines may stimulate or inhibit the release of other cytokines (e.g. IL-10 inhibits IFN-γ secretion from Th1 cells and IL-12 from dendritic cells). The balance between Th1 and Th2 cells and the cytokines and chemokines released in response to selected stimulus can have an important role in how the body's immune system responds to disease. For example, IFN-α may inhibit hepatitis C, and MIP-1α and MIP-1β (also known as CCL3 and CCL4 respectively) may inhibit HIV-1 infection. Optimal balancing of the Th1/Th2 immune response presents the opportunity to use the immune system to treat and prevent a variety of diseases.
The Th1 immune response can be induced in mammals for example by introduction of bacterial or synthetic DNA containing unmethylated CpG dinucleotides, which immune response results from presentation of specific oligonucleotide sequences (e.g. unmethylated CpG) to receptors on certain immune cells known as pattern recognition receptors (“PRR”s). Certain of these PRRs are Toll-like receptors (TLRs).
Toll-like receptors (TLRs) are intimately involved in inducing the innate immune response in response to microbial infection. In vertebrates, a family of ten proteins called Toll-like receptors (TLR1 to TLR10) is known to recognize pathogen associated molecular patterns. Of the ten, TLR3, 7, 8, and 9 are known to localize in endosomes inside the cell and recognize nucleic acids (DNA and RNA) and small molecules such as nucleosides and nucleic acid metabolites. TLR3 and TLR9 are known to recognize nucleic acid such as dsRNA and unmethylated CpG dinucleotide present in viral and bacterial and synthetic DNA, respectively. Bacterial DNA has been shown to activate immune system and antitumor activity (Tokunaga T et al., J Natl Cancer Inst (1984) 72:955-962; Shimada S, et al., Jpn H cancer Res, 1986, 77, 808-816; Yamamoto S, et al., Jpn. J. Cancer Res, 1986, 79, 866-73; Messina, J, et al., J Immunol (1991) 147:1759-1764). Other studies using antisense oligonucleotides containing CpG dinucleotides have shown stimulation of an immune response (Zhao Q, et al., Biochem Pharmacol 1996, 26, 173-82). Subsequent studies showed that TLR9 recognizes unmethylated CpG motifs present in bacterial and synthetic DNA (Hemmi H, et al., Nature (2000) 408:740-5). Other modifications of CpG-containing phosphorothioate oligonucleotides can also affect their ability to act as modulators of immune response through TLR9 (see, e.g., Zhao et al., Biochem Pharmacol (1996) 51:173-182; Zhao et al., Biochem Pharmacol (1996) 52:1537-1544; Zhao et al., Antisense Nucleic Acid Drug Dev (1997) 7:495-502; Zhao et al., Bioorg Med Chem Lett (1999) 9:3453-3458; Zhao et al., Bioorg Med Chem Lett (2000) 10:1051-1054; Yu et al., Bioorg Med Chem Lett (2000) 10:2585-2588; Yu et al., Bioorg Med Chem Lett (2001) 11:2263-2267; and Kandimalla et al., Bioorg. Med. Chem. (2001) 9:807-813). In addition, structure activity relationship studies have allowed identification of synthetic motifs and novel DNA-based structures that induce specific immune response profiles that are distinct from those resulting from unmethylated CpG dinucleotides. (Kandimalla E R, et al., Proc Natl Acad Sci USA. (2005) 102:6925-30. Kandimalla E R, et al., Proc Natl Acad Sci USA. (2003) 100:14303-8. Cong Y P, et al., Biochem Biophys Res Commun (2003) 310:1133-9. Kandimalla E R, et al., Biochem Biophys Res Commun (2003) 306:948-53. Kandimalla E R, et al., Nucleic Acids Res. (2003) 31:2393-400. Yu D, et al., Bioorg Med Chem (2003) 11:459-64. Bhagat L, et al., Biochem Biophys Res Commun (2003) 300:853-61. Yu D, et al., Nucleic Acids Res. (2002) 30:4460-9. Yu D, et al., J Med Chem (2002) 45:4540-8. Yu D, et al., Biochem Biophys Res Commun (2002) 297:83-90. Kandimalla E R, et al., Bioconjug Chem (2002) 13:966-74. Yu D, K et al., Nucleic Acids Res. (2002) 30:1613-9. Yu D, et al., Bioorg Med Chem (2001) 9:2803-8. Yu D, et al., Bioorg Med Chem. Lett. (2001) 11:2263-7. Kandimalla E R, et al., Bioorg Med. Chem. (2001) 9:807-13. Yu D, et al., Bioorg Med Chem Let (2000) 10:2585-8, Putta M R, et al., Nucleic Acids Res (2006) 34:3231-8).
Oligonucleotides and oligodeoxynucleotides containing a ribose or deoxyribose sugar have been used in a wide variety of fields, including but not limited to diagnostic probing, PCR priming, antisense inhibition of gene expression, siRNA, microRNA, aptamers, ribozymes, and immunotherapeutic agents based on Toll-like Receptors (TLRs). More recently, many publications have demonstrated the use of oligodeoxynucleotides as immune modulatory agents and their use alone or as adjuvants in immunotherapy applications for many diseases, such as allergy, asthma, autoimmunity, inflammatory diseases, cancer, and infectious disease (Marshak-Rothstein A, Nat Rev Immunol (2006) 6:823-35).
As a result of their involvement in regulating an inflammatory response, TLRs have been shown to play a role in the pathogenesis of many diseases, including autoimmunity, infectious disease and inflammation (Papadimitraki et al. (2007) J. Autoimmun 29: 310-318; Sun et al. (2007) Inflam Allergy Drug Targets 6:223-235; Diebold (2008) Adv Drug Deliv Rev 60:813-823; Cook, D. N. et al. (2004) Nature Immunol 5:975-979; Tse and Horner (2008) Semin Immunopathol 30:53-62; Tobias & Curtiss (2008) Semin Immunopathol 30:23-27; Ropert et al. (2008) Semin Immunopathol 30:41-51; Lee et al. (2008) Semin Immunopathol 30:3-9; Gao et al. (2008) Semin Immunopathol 30:29-40; Vijay-Kumar et al. (2008) Semin Immunopathol 30:11-21). While activation of TLRs is involved in mounting an immune response, an uncontrolled stimulation of the immune system through TLRs may exacerbate certain diseases in immune compromised subjects. In recent years, several groups have shown the use of synthetic oligodeoxyoligonucleotides (“ODNs”) as inhibitors of inflammatory cytokines (Lenert, P. et al. (2003) DNA Cell Biol. 22(10):621-631).
In addition, several groups have used synthetic oligodeoxynucleotides having two triplet sequences, a proximal “CCT” triplet and a distal “GGG” triplet, a poly “G” (e.g. “GGGG” or “GGG”) or “GC” sequences that interact with TLR proteins to inhibit its activation and the concomitant production and release of pro-inflammatory cytokines (see for example: Lenert, P. et al. (2003) DNA Cell Biol. 22(10):621-631; Patole, P. et al. (2005) J. Am. Soc. Nephrol. 16:3273-3280), Gursel, I., et al. (J. Immunol, 171: 1393-1400 (2003), Shirota, H., et al., J. Immunol, 173: 5002-5007 (2004), Chen, Y., et al., Gene Ther 8: 1024-1032 (2001); Stunz, L. L., Eur. J. Immunol. 32: 1212-1222 (2002; Kandimalla et al. WO2007/7047396). However, oligonucleotides containing guanosine strings have been shown to form tetraplex structures, act as aptamers and inhibit thrombin activity (Bock L C et al., Nature, 355:564-6, 1992; Padmanabhan, K et al., J Biol. Chem., 268(24):17651-4, 1993). Thus, the utility of these inhibitory oligodeoxynucleotide molecules may not be achievable in patients.
Moreover, recent studies have called into question the view that poly G containing ODNs are acting as antagonists of TLRs. For example, U.S. Pat. No. 6,426,334, Agrawal et al., demonstrate that administering CpG oligonucleotides containing “GGGG” strings will cause an increase in serum IL-12 concentration, which demonstrates TLR activation as opposed to TLR inhibition. Further, CpG oligos containing polyG sequences are known to induce immune responses through activation of TLR9 (Verthelyi D et al, J Immunol 166, 2372, 2001; Gursel M et al, J Leukoc Biol, 71, 813, 2001, Krieg A et al, Eur J Immunol, 31, 2154, 2001) and show antitumor and antiviral activities (Ballas G K et al, J Immunol, 167, 4878, 2001; Verthelyi D et al, J Immunol, 170, 4717, 2003). In addition, ODNs containing an immune stimulatory CpG motif and 4 consecutive G nucleotides (class A ODNs) induce interferon-γ production and a Th1 shift in the immune response
Recently, Agrawal et al. (WO2007047396) discovered a novel class of TLR antagonists that do not possess the limitations of previously identified TLR antagonists. Such novel class of compounds effectively inhibits the activity of TLRs and block various TLR agonist activity. However, in some disease states it may be desirable to only partially antagonize TLR activity. Thus, there is a need for compounds that can antagonize TLR activity in a dose-dependent, less than full manner.